Illumination devices based on semiconductor light sources, such as light-emitting diodes (LEDs), offer a viable alternative to traditional fluorescent, HID, and incandescent lamps. Functional advantages and benefits of LEDs include high energy conversion and optical efficiency, durability, lower operating costs, and many others. Recent advances in LED technology have provided efficient and robust lighting units that enable general illumination, as well as a variety of lighting effects in many applications. Some of these lighting units employ two or more groups or “channels” of LEDs which produce light of different colors, each controllably supplied with the predetermined current to enable generation and mixing of light to produce general illumination with desired attributes or a desired lighting effect.
Some of the known LED-based approaches for replacing incandescent light bulbs have a number of shortcomings. For example, one such lamp, shown in FIG. 1A, has a bulb mounted on a socket. A light source, comprising a plurality of LEDs mounted on a PCB, is arranged inside the bulb. The PCB is provided with venting holes that function as cooling means (not shown). A part of the PCB is formed as a base plate on which the bulb, embodied as a protective dome, is mounted, said dome surrounding the light source and parts of the PCB and the cooling means. The dome has a translucent outer surface for transmitting light originating from the light source during operation of the lamp. A lamp axis extends through a central end of the socket and a central extremity of the bulb. The desired omnidirectional light distribution of this lamp is impeded by the base plate on which the dome is mounted. Furthermore, disposing the protective dome over the PCBs and LEDs compromises heat dissipation.
Referring to FIG. 1B, another known LED-based alternative to incandescent light bulbs, particularly A55 and A60 types, is a MASTER LEDbulb available from Koninklijke Philips Electronics N.V., featuring a plurality of LED light sources disposed over a heat sink and emitting dimmable light towards a diffusing dome cover.
Recently, legislation has been enacted to spur development of ultra-efficient solid-state lighting products to replace the common light bulb. The legislation challenges industry to develop viable replacement technologies for two of today's most widely used and inefficient technologies −60 W incandescent lamps and PAR 38 halogen lamps.
Accordingly, it would be desirable to provide an improved lighting device employing LED light sources, optionally addressing one or more of the drawbacks of conventional technologies, while providing quality illumination with high color rendering. It is also desirable for this lighting device to optionally substantially retain commonly encountered form factors, so that existing hardware, sockets, and power connections could be employed, thereby further reducing costs and reducing waste associated with retooling, and facilitating adoption of this improved LED-based electric lamp.